The SNP score did, however, show significant effects in the subsample of current smokers, consistent with the ascertainment method used by the meta-analysis from which the SNP score was derived. Results are given in Table 2. The effect was strongest for later ages with regression coefficients of .021 and .014 at ages 20 and 24, accounting for 1.0% of the variance at age 20 and 0.4% at age 24. While the score was not significant for younger ages, the regression coefficients were in the same direction but of a smaller magnitude (.010 and .009 at age 14 and 17). The SNP score at age 14 and 17 accounted for 0.1% to 0.4% of the variance, respectively, suggesting an attenuation of effect instead of the lack of effect. A composite test of the null hypothesis that the regression coefficient was the same at all ages approached statistical significance (Χ2 = 6.2, df =3, p = .10).
